1. Geometry Vocabulary 2.7
Substitution Property: When pairs of angles or segments are congruent to each other, one may be substituted into any statement for the other.
Given:
Conclusion:
Reason:

2. Transitive Properties
Thm. 16: If angles or segments are congruent to the same angle or segment, they are congruent to each other.
Example:

3. Thm. 17: If angles or segments are congruent to congruent angles or segments, they are congruent to each other.
Example:

4. Geometry Vocabulary 2.8
Opposite rays: Two collinear rays that have a common endpoint and extend in different directions are called opposite rays.
Example:

5. Vertical angles: Two angles are vertical angles if the rays forming the sides of one and the rays forming the sides of the other are opposite rays.
Thm. 18 Vertical angles are congruent.
Example:

6. Sample Problems
Given:
Prove:

7. Given:
Prove:

8. Given:
Find: